A basic and yet highly sophisticated function of the nervous system is the control of movement This application proposes a study of the neuromuscular control of hand movements, gestures of the proximal arm, and whole-body reaching. The objective is to uncover the fundamental characteristics of muscular synergies. There are three aims:Aim 1 is to test the distributed nature of motor unit activation. It is a study of the recruitment and firing characteristics of single motor units in hand muscles, aimed at distinguishing between a compartmentalized and a distributed organization.Experiment la looks at the control of force direction during grasping; Experiments 1b and 1c involve a wide variety of hand shapes and sequences of hand movement. Aim 2 is to determine the degree to which motor control is continuous or segmented. Arm kinematics and surface electromyographic (EMG) activity will be recorded during an arm movement task that resembles making gestures in 3D space. In Experiment 2, the degree of segmentation will be quantified, and the EMG analysis will be aimed at identifying a basic repeating unit, Experiment 2 will also test for look-ahead planning in the construction movement sequences. Aim 3 is to study head and arm coordination in a whole-body reaching task. Head and arm kinematics will be recorded along with the EMG activity of neck and shoulder muscles. The aim is to describe the temporal pattern, look for basic synergies, and further test the hypothesis of distributed activation.All three aims are based on a hypothesis that stemmed from the results of the previous funding period. These results suggested that point-to-point reaching movements are controlled via a continuous comparison of current and desired arm postures. Furthermore, the results showed that the pattern of motor unit activation is highly distributed (within and across muscles) and unfolds in a continuous fashion as the movement proceeds. This hypothesis differs from older views that simple movements are largely preplanned, and that execution is at the level of discrete neuromuscular compartments, whole muscles, or synergies involving groups of muscles. If this new hypothesis is supported it will have direct implications for efforts in prosthetics